The only overriding reason I can see (as a PC user) is that there is some design/development software (CodeKit for example) that isn’t available for non-Mac users.
Where there is software available on both platforms then there is no effective difference (at least as far as I can tell). Does it LOOK better on a retina mac…sure, but then everything does. :)
As to the question do you NEED a Mac….then the answer is NO.
Do you want a Mac (and getting to relearn how things are just slightly different from the PC worls)…that’s up to you.